JP-A-53-77057 discloses a process for the preparation of 1,2-benzisoxazole-3-methanesulfonamide from 1,2-benzisoxazole-3-acetic acid as a starting compound. In this process, the intermediate, sodium 1,2-benzisoxazole-3-methanesulfonate, is isolated in solid form from a water layer, and there is a removal operation of insoluble material from a reaction mixture. Processes for the preparation of 1,2-benzisoxazole-3-methanesulfonamide comprising a reaction of isolated sodium 1,2-benzisoxazole-3-methanesulfonate in solid form are disclosed in U.S. Pat. No. 4,172,896, JP-A-54-163823 and Uno, et al., J. Med. Chem., 22,180 (1979). A. Mustafa et al., Tetrahedron, 19, 1831 (1963), G. Casini, et al., J. Heterocycl. Chem., 6, 279 (1969), M. Giannella, et. al., Phytochemistry, 10, 539 (1971), P. Thourel, et al., J. Labell. Compd. Radiopharm., 25, 1235 (1988), US 2002/0183525 A1 and US 2004/0049053 A1 disclose a process for the preparation of 1,2-benzisoxazole-3-acetic acid or its derivatives from 4-hydroxycoumarin or its derivatives. However, these literatures disclose neither a reaction using only water as a solvent nor a reaction involving a chelating agent. US 2003/0114682 A1 and US 2003/0144527 A1 disclose a process for the preparation of sodium 1,2-benzisoxazole-3-methanesulfonate from 1,2-benzisoxazole-3-acetic acid. US 2004/0014983 A1 discloses processes for the preparation of 1,2-benzisoxazole-3-methanesulfonyl chloride from sodium 1,2-benzisoxazole-3-methanesulfonate, and 1,2-benzisoxazole-3-methanesulfonamide from 1,2-benzisoxazole-3-methanesulfonyl chloride. In M. Shimizu, et al., Yakugaku-Zasshi, vol. 116, p. 533-547 (1996), an industrial process for the preparation of 1,2-benzisoxazole-3-methanesulfonamide via 1,2-benzisoxazole-3-acetic acid, sodium 1,2-benzisoxazole-3-methanesulfonate and 1,2-benzisoxazole-3-methanesulfonyl chloride as an intermediate is disclosed using 4-hydroxycoumarin as a starting compound. However, these literatures do not disclose a one-pot process for the preparation of 1,2-benzisoxazole-3-methanesulfonamide using 4-hydroxycoumarin or 1,2-benzisoxazole-3-acetic acid as a starting compound without isolating intermediates in solid form.